Is there a limit to the number of users I can set up for my business? firm of accountants with staff I'm trying to add as users but they are not getting the invite email?

Hello Clarej1, There is no limited for accountants to be added to firms. However they may be needed to be added to the safe senders list for the employees as it may be in the spam folder.  You can have a look at these 2 articles it tells you more 

3 solutions for you when customers aren't receiving your emails

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